Objective　To explore the clinical characteristics, gene mutation and prenatal gene diagnosis of primary carnitine deficiency. Method　The clinical data and the results of gene mutation analysis of primary carnitine deficiency in 8 children as well as the prenatal genetic diagnostic results of amniotic fluid cells in her second pregnancy of a mother were retrospectively analyzed. Results　Six boys and two girls, aged from 5 months to 3 years, visited for vomiting, diarrhea, convulsions and disturbance of consciousness. The plasma free carnitine concentrations were reduced (0.67~4.184 μmol/L) and the hemoglobin concentrations were also decreased (67~110 g/L) in all children. There were abnormalities in liver function and myocardial enzymes in 6 cases, elevated blood ammonia in 6 cases and decreased blood sugar in 2 cases. Cardiomyopathy was indicated by color Doppler echocardiography in 4 cases. Two cases had abnormal electrocardiogram. Six mutations were detected in SLC22A5 gene, including c.760C>T (p.Arg254X), c.1400C>G (p.Ser467Cys), c.844dupC (p.R282PfsX10), IVS2+1G>T, c.3G>T (p.Met1Ile), and c.338G>A (p.Cys113Tyr). A large heterozygous deletion in the 5q23.3q31.3 region was found by chromosome microarray analysis in a child. The c.760C>T heterozygous mutation was detected in amniotic fluid cells of the mother at 18 weeks of second pregnancy, suggesting that the fetus was a carrier. There was a c.760C>T heterozygous mutation site in the peripheral blood SLC22A5 gene analysis after birth, and plasma free carnitine concentration was normal. Except for one case of sudden death, the other 7 cases were treated effectively with L-carnitine, and were under followed-up. Conclusion Primary carnitine deficiency have acute onset, and myocardial and liver injury are particularly prominent. L-carnitine has a good therapeutic effect in primary carnitine deficiency. SLC22A5 gene analysis can be used for the diagnosis and prenatal diagnosis.